Preparing a Wet Mount
Using a pipet or dropper, add a drop of water or
another solvent to a clean microscope slide.
Then, place the specimen in the water.
Place the edge of a coverslip on the slide so that
it touches the edge of the water.
Slowly lower the coverslip to prevent the
formation of air bubbles.
increases visibility of specimen
accentuates specific morphological features
Process by which internal and external
structures are preserved and fixed in
position. Organisms are also killed and
firmly attached to microscope slide.
▪ preserves overall morphology but not internal
▪ protects fine cellular substructure and morphology
of larger, more delicate organisms
make internal and external structures of cell
more visible by increasing contrast with
have two common features
▪ chromophore groups
▪ chemical groups with conjugated double
▪ give dye its color
▪ ability to bind cells
a single staining agent is used
basic dyes are frequently used
▪ dyes with positive charges
▪ e.g., crystal violet
divides microorganisms into groups based on
their staining properties
e.g., Gram stain
e.g., acid-fast stain
most widely used differential staining
divides Bacteria into two groups based on
differences in cell wall structure